, 1996, Hooten and Highsmith, 1996, Dean et al., 2000, Bodkin et al., 2002, Huggett et al., 2003, Short et al., 2006 and Esler and Iverson, 2010). Investigators TGF-beta inhibitor established campsites and ran boats in and out of this area for two decades. In other parts of PWS, otters tended to leave areas with high boat traffic ( Garshelis and Garshelis, 1984). Bodkin et al. (2011) suggested that the disturbance from a new fishery contributed to many otters leaving the Montague Island survey areas in 2009 ( Fig. 3a). Notably, the various post-spill sea otter studies involved capturing, immobilizing, and surgically implanting radio-transmitters in

over 200 individuals at NKI (out of a population averaging less than 80 individuals, but with substantial individual turnover), adding more disturbance learn more (and direct stress) to sea otters in the study site. The initial recovery target for sea otters, developed by the Exxon Valdez Oil Spill Trustee Council (1994: 52) was defined as “when population abundance and distribution are comparable to pre-spill abundance and distribution, and when all ages appear healthy.” They also added this caveat: “Exactly what population increases would constitute recovery is very uncertain, as there are no population

data from 1986 to 1989, and the population may have been increasing in Eastern Prince William Sound during that time.” The recovery goal has since been modified to “a return to conditions that would have existed had the spill not occurred” (Exxon Valdez Oil Spill Trustee Council, 2006: 4). This is even more difficult to assess, as it requires knowledge of pre-spill conditions as well as the ability to predict what would have occurred over the next several decades in terms of Rolziracetam otter abundance

and distribution with changing conditions but absent the spill. We contend that such predictions are unreasonable in complex biological systems like this, which are subject to numerous confounding variables, most of which are not quantifiable, except in a relative sense (Harwell et al., 2010b). Confounding variables are the nemesis of any study investigating the effects of an environmental event on wildlife populations (Wiens and Parker, 1995). Limited data were available for sea otters in PWS before the oil spill, and no truly valid control sites existed after the spill. Compared to a selected reference site at Montague Island, the Knight Island area has much less kelp (preferred otter resting habitat), deeper nearshore waters (and therefore less feeding habitat for pups), higher human subsistence harvests, more killer whales (due to the deeper waters), and direct evidence of recent predation on otters by these whales. Moreover, whereas some studies concluded that otters moved between the reference and treatment areas (e.g., source–sink model; Monson et al.